1. Field of the Invention
The invention relates in general to a storage system, and in particular to a storage system using semiconductor memories, such as flash memories, for storage devices.
2. Description of Related Art
Storage control systems include storage systems and information processors that serve as host systems for the storage systems. The storage systems house storage devices such as hard disk drives in arrays, thereby providing a sufficient storage capacity to the information processors. The information processors are connected to the storage systems via SANs or the like and write data in, and read the written data from, the storage devices. The storage systems include controllers for controlling data transmission between the storage devices and information processors.
Because the data in the hard disk drive can be rewritten whenever necessary, there is a risk of it being tampered with. Conventional art for storage systems includes those with a data rewrite protection function. The data rewrite protection function is called WORM (Write Once Read Many).
For example, Japanese Patent Laid-Open Publication No. 2005-267602 discloses a storage system capable of protecting data stored in the volumes in the storage system. This storage system includes storage media for providing volumes, a disk controller for controlling the storage system, and a WORM (recordable) structure table having a plurality of entries where the areas that are write-protected, from among a plurality of areas in volumes, are displayed with next-write-area indicating pointers, so that it can manage these protected areas, thereby implementing the WORM functionality. The entries in the WORM structure table indicate the write-protected areas in the volumes, which are defined by top offsets and end offsets.
Japanese Patent Laid-Open Publication No. 2005-284816 discloses a storage system that realizes WORM functionality with its entire system including cache memory. This storage system includes storage devices for storing write data received from computers, cache memory, and a controller that controls the input/output of data to/from the storage devices. The controller judges whether or not write data has already been written in a write destination storage area designated by a write command from the computer, and if write data has not yet been written in the write destination storage area, the controller receives the write data in accordance with the write command and stores it in the cache memory.
Japanese Patent Laid-Open Publication No. 2005-338945 also discloses a storage system realizing WORM functionality. In this storage system, when a data write request is received from a computer, whether or not write target data sent from the computer can be written is judged based on the content indicated in write protection information. If the write target data can be written, a guarantee code is created for the sent data; write protection information indicating that the area the write target data is to be stored in is a write-protected area is created; the created write protection information is stored in the guarantee code; the guarantee code storing the write protection information is given to the area the write target data received from the computer is to be stored in; and the data having the guarantee code storing the write protection information is stored in the cache memory and/or disks. If the write target data from the computer cannot be written, the computer is notified to that effect.
However, in these conventional storage systems, the storage devices themselves do not have the WORM functionality; instead the management software provided by the storage systems' vendors provides the WORM functionality to the storage systems. Accordingly, for those conventional storage systems, no consideration has been made for physical prevention of data tampering in storage devices such as CD-Rs and DVD-Rs.
In storage systems, because the data issued from information processors and written in storage devices requires frequent updating, it is a matter of course that the storage resources cannot be composed only of one-time recordable storage devices. Therefore, one-time recordable storage devices and anytime-rewritable storage devices are used together and data that should be protected from being tampered with is migrated to the recordable storage devices; however, such use of recordable storage resources as storage resources is not efficient.
In order to solve these problems, this invention aims to provide a storage system where storage devices themselves have WORM functionality that an administrator can set as required.